London, Jan 8 (ANI): A 'restricted' memo of UK's Department for Transport has revealed that al Qaeda's 'international operations wing' is plotting one or more Mumbai-style terror attacks in Europe, including the UK.

"It is assessed that AQ continues to seek to conduct attacks that have a significant political, economic or psychological impact and that result in a large number of casualties," The Daily Mail quoted the document, as saying.

The document also said that the threat is 'credible' and would be designed to claim a 'large number of casualties'. It claimed that methods like deploying car bomb or using 'firearms against aircraft and airport targets', similar to the Mumbai machine-gun attacks of 2008, could be a part of their strategy.

"Whilst there are a number of ways in which AQ could achieve such an impact, there are indications that they may be considering an attack against a UK airport or aviation sector target," it added.

Meanwhile, Whitehall officials have said that although the terror threat remains 'severe' for the whole nation, there is no evidence that the attack is imminent.

They further claimed that any firm information of such a plot would alarm the authorities to raise the threat level to 'critical', the most severe of the five levels that warn the public of the threat from international terrorism.

However, the memo reveals there has been sufficient concern to issue a specific alert to Britain's airports and to rail bosses in London. Some police leave has been cancelled in the capital, and extra officers are being deployed at airports and rail stations, the paper said.

There have been concerns in recent months over the possibility of Mumbai-style terror attacks in Europe.

Earlier, two former SAS commanders had warned that if terrorists did manage a Mumbai-type strike in Britain, the country would face a 'slow motion' September 11. (ANI)